1. Field of the Invention
The present invention relates to a piezoelectric/electrostrictive device that is provided with a movable section to be operated on the basis of a displacement action of a piezoelectric/electrostrictive element, or a piezoelectric/electrostrictive device that is capable of detecting displacement of a movable section by the aid of a piezoelectric/electrostrictive element, and a method of producing the same. In particular, the invention relates to a piezoelectric/electrostrictive device that is excellent in strength, shock resistance, and moisture resistance and that makes it possible to efficiently operate a movable section to a great extent, and a method of producing the same.
2. Background of the Invention
Recently, a displacement element, which makes it possible to adjust the optical path length and the position in an order of submicron, is demanded, for example, in the fields of optics, magnetic recording, and precision machining. Development is advanced for the displacement element based on the use of the displacement brought about by the inverse piezoelectric effect or the electrostrictive effect caused when a voltage is applied to a piezoelectric/electrostrictive material (for example, a ferroelectric material).
As shown in FIG. 23, for example, those hitherto disclosed as such a displacement element include a piezoelectric actuator comprising a fixing section 204, a movable section 206, and a beam section 208 for supporting the fixing and movable sections, which are formed integrally with a hole 202 provided through a plate-shaped member 200 composed of a piezoelectric/electrostrictive material and with an electrode layer 210 provided on the beam section 208 (see, for example, Japanese Laid-Open Patent Publication No. 10-136665).
The piezoelectric actuator is operated such that when a voltage is applied to the electrode layer 210, the beam section 208 makes expansion and contraction in a direction along a line obtained by connecting the fixing section 204 and the movable section 206 in accordance with the inverse piezoelectric effect or the electrostrictive effect. Therefore, the movable section 206 can perform circular arc-shaped displacement or rotational displacement in the plane of the plate-shaped member 200.
On the other hand, Japanese Laid-Open Patent Publication No. 63-64640 discloses a technique in relation to an actuator based on the use of a bimorph. In this technique, the electrodes of the bimorph actuator are provided in a divided manner. The actuator is driven due to the selection of the divided electrodes, and thus highly accurate positioning is performed at a high speed. JP '640 discloses a structure (especially in FIG. 4) in which, for example, two opposed bimorphs are used.
However, the piezoelectric actuator described above involves a problem that the amount of operation of the movable section 206 is small, because the displacement in the direction of extension and contraction of the piezoelectric/electrostrictive material (i.e., in the in-plane direction of the plate-shaped member 200) is transmitted to the movable section 206 as it is.
Since all the parts of the piezoelectric actuator are made of piezoelectric/electrostrictive materials, which are fragile materials having a relatively heavy weight, the mechanical strength is low, and the piezoelectric actuator is inferior in handling performance, shock resistance, and moisture resistance. Furthermore, the piezoelectric actuator itself is heavy, and its operation tends to be affected by harmful vibrations (for example, residual vibration and noise vibration during high speed operation). In particular, the piezoelectric actuator has a weakness for torsion.
Then, a method may be adopted which increases the strength and the resonant frequency by thickening a beam portion, for example, in order to improve stiffness. However, displacement and a response speed are significantly deteriorated due to the improvement of stiffness.